Magnetic tape is commonly used for storage of digital data. The digital data is accessed by a data transfer apparatus, which can perform one or both of storing (writing) data onto the tape, or accessing (reading) data previously stored on the tape. A generic term for a magnetic tape data transfer apparatus is a “tape drive.” A tape drive normally includes a tape head for one or both of reading and/or writing data from or to the magnetic tape. The tape head itself includes one or more tape head elements, which can perform one or both of these functions.
One type of head used in tape drives is a rotary scan head (also known as a helical scan head). Typically, the rotary scan head is in the form of a drum 80. As shown in FIG. 1, the drum 80 has one or more head elements 90 positioned on its cylindrical surface for performing read and/or write operations. During a loading process of a tape cartridge holding tape for use by the tape drive, a portion of the tape 100 is deployed around the drum 80. During reading and/or writing, the tape 100 is moved in a direction A whilst the drum 80 rotates about an axis B. The drum 80 typically rotates much faster that the speed of movement of the tape 100 so that tracks 101 can be read from, or written to, the tape 100 by the head element 90.
Tape drives using a rotary scan head typically include one or more tape guides in the form of a tape guide assembly. An example tape cartridge 110 and guide assembly 10 for a tape drive is shown in FIGS. 2 and 2a. The tape guide assembly 10 is used to deploy the tape 100 from within the tape cartridge 110 so that at least a portion of the tape is threaded around at least part of the drum 80. The tape guide assembly 10 is also used during reading and/or writing to direct, align, and support the tape 100 as it is moved across the drum 80. The tape guides can either be fixed or stationary guides, such as spindles, or rollers, which roll with the tape as the tape moves across the tape head. The tape guides help to align the tape 100 with respect to the drum 80 and may also include flanges 45, 50 to prevent excess lateral movement of the tape. The guides can include powered rollers to assist in transport of the tape across the drum and to provide proper tensioning of the tape.
The guide assembly 10 shown in FIGS. 2 and 2a includes tape guides in the form of a capstan 30, a pinch roller 20, a number of guide posts 40, 50, and a number of inclined posts 60, 70. The guide posts 40, 50 and pinch roller 20 engage the tape 100 within a tape cartridge 110 or other carrier during a loading process. During a deployment process, the guide posts 40, 50 and pinch roller 20 are moved from their respective non-deployed positions (shown in FIG. 2) engaging the tape 100 and moving along predetermined guide travel paths to respective deployed positions (shown in FIG. 2a). In this manner, a portion of the tape 100 is extracted from the tape cartridge 110 and is deployed around the drum 80. In its deployed position, the tape 100 is sandwiched by the capstan 30 and the pinch roller 20.
Flanges 45, 55 are typically provided on the top and bottom of the guide posts 40, 50 respectively to restrict lateral movement of the tape 100 with respect to the drum 80. The inclined post 60 is positioned so as to incline the tape with respect to drum 80 when threading onto the drum 80 and the inclined post 70 is positioned to return the tape 100 to the non-inclined position when threading off of the drum 80.
Rotary scan tape drives are designed to use a predetermined size and type of tape cartridge that contains a predetermined length of a predetermined width tape. In this manner, the designer of the tape drive knows the size of the cartridge and the width (w) of tape that must be accommodated and can therefore dimension and position the tape guides and flanges appropriately. The width (w) of the tape typically corresponds to the height (h) of the tape guides, so that the tape is aligned with respect to the drum 80 and its head element(s) 90 by the flanges 45, 55 of the guides.
One format for data storage using a rotary scan tape drive is Digital Data Storage (DDS). Various versions of DDS exist and although each version uses the same (approximately 4 mm) width tape in the same Digital Audio Tape (DAT) cartridges, increasingly advanced reading and writing techniques have been used in later versions to achieve greater data storage capacity from the same media as earlier versions. Customers are demanding more and more data storage capacity and in the past, the use of such advanced reading and writing techniques have addressed (at least to some extent) those demands. However, for practical purposes, the storage capacity of a given size of tape is ultimately limited by the available surface area of the tape.
Instead of trying to cram more data onto the same sized tape, one option is to apply the DDS reading and writing techniques to different width tapes. Whilst a greater width tape inherently provides more storage capacity due to the increased surface area available, tape drives and in particular their guide assemblies are currently limited to a single tape cartridge size that holds tape of a predetermined width, which requires that a new tape drive be produced for each different tape width. Not only does this mean increased expense for the user, it also means that existing tapes would not be compatible with the new drives and would require the user to transfer any existing stored data to new tape media or, alternatively, to maintain two tape devices.
One problem faced with tape drives that attempt use of multiple tape widths is encountered during extraction of the tape from its cartridge. Typically, in order to allow a tape cartridge to be loaded into a tape drive, the non-deployed positions of the guides are normally designed so that the guides fit within a cavity 125 in the cartridge 110, when loaded, as is shown in FIG. 2b. The guides are then moved to their deployed positions. In the case of a single tape width, this arrangement is relatively simple to achieve as the height of the guides can be selected to fit the tape width (which the cartridge must inherently be high enough to hold). However, where a tape drive uses multiple tape widths, the height of the cartridge itself may vary, in which case a standard height for guides is not possible. If a tape guide was positioned in its non-deployed position to align itself with the top and bottom edges of the tape then it would be too high to fit in a cavity of a smaller cartridge shell. Alternatively, if a tape guide is dimensioned to avoid hitting the smaller cartridge shell, it would not engage the full width of a larger width tape in the deployed position.
In order to address this issue, various complex sensing arrangements have been suggested so that a predetermined height may be used for tape guides for each cartridge size so as to accommodate each tape width. However, such arrangements require additional mechanisms, sensors, and control systems and increase the complexity and cost of the tape drives. Where tape guides such as the pinch roller are lowered or raised into position after threading, clearance must be provided to allow the tape to be threaded over or under the tape guide.
Thus, a heretofore unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.